/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.state;



import com.bff.gaia.unified.sdk.annotations.Internal;

import com.bff.gaia.unified.sdk.transforms.windowing.TimestampCombiner;

import org.joda.time.Instant;



/**

 * <b><i>For internal use only; no backwards-compatibility guarantees.</i></b>

 *

 * <p>A {@link State} accepting and aggregating timestamps according to a {@link TimestampCombiner},

 * holding the output watermark to the resulting timestamp.

 */

@Internal

public interface WatermarkHoldState extends GroupingState<Instant, Instant> {

  /**

   * Return the {@link TimestampCombiner} which will be used to determine a watermark hold time

   * given an element timestamp, and to combine watermarks from windows which are about to be

   * merged.

   */

  TimestampCombiner getTimestampCombiner();



  @Override

  WatermarkHoldState readLater();

}